The conventional alkaline cyanide metal plating process includes the steps of plating metal articles in an alkaline cyanide plating bath, (for example, a cyanide zinc or cyanide cadmium alkaline plating bath), removing and rinsing each article in water, and chlorinating the rinse water to remove cyanide and other contaminants. For a description of the conventional chlorination step, see the commercial bulletin entitled "The Chemical Destruction of Common Plating Room Waste", The Harshaw Chemical Company, 1972. During the plating of metal articles in alkaline cyanide plating systems, ferrocyanide ions built up with other cyanide ions. The ferrocyanide ions, unlike most other metal cyanide ions are not destroyed when rinse water is treated by conventional chlorination methods. Prior to the present invention, no economical, effective process has been known for removing the ferrocyanide ions from rinse water of an alkaline cyanide metal plating bath. It would be highly desirable to have an economical, effective process for removal of ferrocyanide ions from rinse water, since these ions when exposed to sunlight are decomposed into cyanide ions which are harmful to plant and animal life.